Stray current corrosion has damaged the chilled water underground piping at several multi-family housing units where I work. The piping has deep metal loss on the lower portion and has pin hole leaks. The hot water piping is not damaged although it runs side by side with the chilled water piping. The four 10HP pumps for the system are 480V 3 PH. Each pump is controlled by a VFD. The service is 120/208V 3PH. and is boosted to each pump via step up XFMRS, one for each pump. Has anyone had experience with this or a simialar condition? Any advice?
Hydronic damage from stray current
- Thread starter chammock
- Start date
- Status
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: Hydronic damage from stray current
plastic does not corrode.
plastic does not corrode.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Re: Hydronic damage from stray current
How do you know it was caused by stray current?
-Hal
How do you know it was caused by stray current?
-Hal
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Re: Hydronic damage from stray current
Ahhh the pipe manufacturer. Betcha the plumber will swear to it too. Any idea where the leakage is coming from? Have YOU performed any tests?
-Hal
Ahhh the pipe manufacturer. Betcha the plumber will swear to it too. Any idea where the leakage is coming from? Have YOU performed any tests?
-Hal
pierre
Senior Member
- Location
- Westchester County, New York
Re: Hydronic damage from stray current
See if you can get a copy of the report, it would be interesting to see their results.
See if you can get a copy of the report, it would be interesting to see their results.
brian john
Senior Member
- Location
- Leesburg, VA
Re: Hydronic damage from stray current
It is unusual for AC ground current to result in pipe damage (I have arrived at this statement by doing online searches and library research for several customers that had similar problems and doing ground investigatioins). There has been extensive research on this subject by several local utilities; Washington Suburban Sanitary Commission has a web site covering this issue.
But if you feel ground current is the cause of this corrosion, look for the source of the current.
Is there ground current present on any of the grounding electrodes conductors, equipment grounding conductors and take zero sequence measurements on the feeders.
Or are you in the vicinity of any DC voltage sources, rail or subways?
It is unusual for AC ground current to result in pipe damage (I have arrived at this statement by doing online searches and library research for several customers that had similar problems and doing ground investigatioins). There has been extensive research on this subject by several local utilities; Washington Suburban Sanitary Commission has a web site covering this issue.
But if you feel ground current is the cause of this corrosion, look for the source of the current.
Is there ground current present on any of the grounding electrodes conductors, equipment grounding conductors and take zero sequence measurements on the feeders.
Or are you in the vicinity of any DC voltage sources, rail or subways?
karl riley
Senior Member
Re: Hydronic damage from stray current
There is some DC produced by electronic power regulators, as verified by the AWWA (American Water Works Association). But I would also look for any other sources of DC.
Karl
There is some DC produced by electronic power regulators, as verified by the AWWA (American Water Works Association). But I would also look for any other sources of DC.
Karl
Re: Hydronic damage from stray current
When using VFD on an ungrounded system pitting of bearings and water pipes is a common occurence, caused by the high frequencies. Many manufacturers will attempt a multitude of grounding solutions, additional grounding electrodes, low resistance paths to the earth etc., but the only reliable answer is to run the VFD on a grounded system - 480Y/277 for example.
When using VFD on an ungrounded system pitting of bearings and water pipes is a common occurence, caused by the high frequencies. Many manufacturers will attempt a multitude of grounding solutions, additional grounding electrodes, low resistance paths to the earth etc., but the only reliable answer is to run the VFD on a grounded system - 480Y/277 for example.
brian john
Senior Member
- Location
- Leesburg, VA
Re: Hydronic damage from stray current
Derf:
Do you know of any documentation or data available on VFD on ungrounded systems?
Derf:
Do you know of any documentation or data available on VFD on ungrounded systems?
- Status